Growth stimulation in animals is expected on the basis of GH protein injection experiments. It has been recognized that the insertion of growth hormone (GH) genes into fish to form transgenic fish should lead to increased growth for such fish. Using mammalian or viral promoters and mammalian GH genes some success was achieved forming transgenic fish in the prior art. However expression of the GH gene was inconsistent and increase in growth was very limited.
The solution to this problem of adequate expression of the transgenes appears to be the identification and thorough characterization of suitable homologous fish promoters for gene transfer involving fish species. "Homologous" is used herein to mean relating to the same fish genus or family. Only a handful of fish promoters have been analyzed for their transcriptional activity using a fish tissue culture or transgenic system. They include the promoters from carp beta-actin; Xiphophorus MT and Xmrk proto-oncogene and oncogene; ocean pout, wolffish, sea raven and winter flounder anti-freeze protein; yellowtail alpha-globin; rainbow trout MT-B; and chinook salmon prolactin. There is clearly a need to increase the pool of well-characterized regulatory DNA sequences that are suitable for gene transfer in fish.
In patent application PCT/CA92/00109, C. L. Hew et al. (published as WO 92/16618 Oct. 1, 1992) there are described gene sequences derived from ocean pout anti-freeze gene promoter and other fish gene sequences including chinook salmon GH gene. Gene transfer of this GH gene to form transgenic Atlantic salmon (Salmo salar) is disclosed. Some evidence is presented in this reference for increased growth rate and earlier smolting for the transgenic Atlantic salmon. Further aspects of this work are described in S. J. Du et al. Bio/Technol. Vol. 10 pp. 176-181 (1992).
Transgenic fish vectors which consist of the carp .beta.-actin or the rainbow trout metallothionein (MT) promoters and the gilthead seabream GH cDNA are described in B. Cavari et al. Fish Physiology and Biochemistry Vol. 11 No. 1-6 pp. 345-352 (1993). In the above referenced studies all or part of the construct was derived from non-homologous genus of fish.
For the highest assurance of acceptance by regulatory authorities and the public, transgenic fish should have all inserted DNA sequences derived from the same fish genus or family.
In order to increase the commercial potential for the application of transgenics to the aquaculture of Salmonidae, it would be significant to provide promoters, vectors and vector-gene constructs homologous to the family Salmonidae.